Problem

I have a problem with writting in js tab in sololearn. I wrote simple input with id and button with function that adds 1 to the value of input with id and it prints me that it can't set value of null https://code.sololearn.com/W1DLAuJajaVB/?ref=app

javascript

14th Nov 2019, 9:27 AM

Patrick Daniel Parafińczuk

1 Respuesta

+ 2

1. If you removed the scripts in the JS tabs, there is no null error, but the result is appending "1" to ones, outcome: "1", "11", "111",.... reason is Type Coercion because the plus operator have method overloading, when both operands are number, it performs Number addition(); however, when one of the operand is string, it performs String.concantenation(). Solution is to convert the type with Number() or parseInt() let curValue = inputDOM.value; curValue = parseInt(curValue); curValue = curValue + 1; https://www.sololearn.com/post/115762/?ref=app 2. Now, back to your null error, because SoloLearn JS tab puts your scripts in <head>, your getElementById() is trying to look for a DOM which has not existed yet, that's why it is null. Solution is to window.onload = function() { your scripts } if you want to put scripts in JS Tab. https://www.sololearn.com/post/90825/?ref=app 3. https://code.sololearn.com/WKKkpq0efxai/?ref=app

14th Nov 2019, 3:13 PM

Gordon